This Bloomberg article describes the unusually high re-election rate for incumbent members of Congress running for re-election last month. Perhaps most surprising is that only one incumbent U.S. Senator was defeated for re-election in the November election (also one incumbent was defeated in a primary earlier in the year).
In the House, only 40 incumbents were defeated, and in 13 of those instances, two incumbents were running against each other, so defeat of an incumbent was inevitable. Thanks to Thomas Jones for the link.